Pope Francis condemned a deadly blast at a church in Egypt and said at a Palm Sunday Mass that the world was suffering from wars, terrorism and "interests that are armed and ready to strike".

Francis, who has not made any direct public comment on the current Middle East crisis, said the Mass as international tensions increased following the U.S. missile strike on a Syrian air base, which the Pentagon says was involved in a chemical weapons attack that killed 87 people.

While the pope, who is due to visit Egypt April 28-29, was celebrating the Mass for tens of thousands of people, the Vatican received word of the blast that killed at least 29 people and injured 70 in a Coptic church in the Nile Delta.

"I pray for the dead and the victims. May the Lord convert the hearts of people who sow terror, violence and death and even the hearts of those who produce and traffic in weapons," he said in hastily prepared comments at the end.

The blast was the latest assault on a religious minority that has increasingly been targeted by Islamist militants.

Palm Sunday, the start of Holy Week that culminates on Easter Sunday, commemorates the day Christians believe Jesus entered Jerusalem and was welcomed as the messiah, only to be crucified five days later.